. sftt y x, scal sigmau(zu) sigmaw(zw) robust nocons ///
>          initial(delta_x 1 du_zu 0.6 mu_u 1 dw_zw 0.8 mu_w 1)
initial value: delta_x 1 du_zu 0.6 mu_u 1 dw_zw 0.8 mu_w 1
{\smallskip}
Iteration 0:  residual SS =  68791.84
Iteration 1:  residual SS =  68791.83
Iteration 2:  residual SS =  68791.83
Iteration 3:  residual SS =  68791.83
{\smallskip}
{\smallskip}
Nonlinear regression                                Number of obs =     10,000
                                                    R-squared     =     0.3221
                                                    Adj R-squared =     0.3217
                                                    Root MSE      =   2.623476
                                                    Res. dev.     =   47663.77
{\smallskip}
{\bftt{Two-tier stochastic frontier model with scaling property}}
\HLI{13}{\TOPT}\HLI{64}
             {\VBAR}               Robust
           y {\VBAR} Coefficient  std. err.      t    P>|t|     [95\% conf. interval]
\HLI{13}{\PLUS}\HLI{64}
    /delta_x {\VBAR}   1.004185    .025706    39.06   0.000     .9537958    1.054574
      /du_zu {\VBAR}   .5945576   .0549976    10.81   0.000     .4867511    .7023641
       /mu_u {\VBAR}   1.013727   .1194433     8.49   0.000     .7795938     1.24786
      /dw_zw {\VBAR}    .777372   .0684228    11.36   0.000     .6432496    .9114945
       /mu_w {\VBAR}   1.030119   .1314907     7.83   0.000     .7723708    1.287867
\HLI{13}{\BOTT}\HLI{64}
